The use of portable spraying devices has been common for years in many industries. Many of these devices are mounted on powered vehicles for movement from one site to another.
For example, German Patent No. DE-PS 30 37 182 discloses a device for mechanically guiding a spray nozzle, more particularly for applying air-placed concrete. The device is brought by transport means to the place of use, where it remains. The arm has a telescopingly extendable prolongation for applying concrete at variable distances from the device. The known device is inexpensive and space-saving and is equipped exclusively with pneumatic drive elements enabling the device to be manipulated very easily, appropriately for its purpose, via a singlehanded lever. The known device is suitable, for example, for spraying conrete onto tunnel arches or embankments, where it is used under normal temperature conditions.
In the steel industry, it is regularly necessary to repair the refractory linings of melting crucibles and melting pots after use; for technical and economic reasons, it is usually impossible to wait until the crucible has sufficiently cooled before starting repairs. Consequently, linings are repaired by using spray lances of adequate length, enabling the staff to carry out repair work from a sufficient distance from the crucibles, which are often still at temperatures above 1000.degree. C. Of course, these lances can only have a small useful spray cross-section; if they are to be manipulated manually by one operator.
On the other hand, the platforms used for making repairs on crucibles are of limited size, so that it is impossible to use large, complicated devices. Admittedly, there is a known heavy hydraulic device for repairing the aforementioned refractory linings, but in most cases it cannot be used owing to lack of space and the disproportionately high cost.